The Hebrew emesh means "yesterday" or "last night," referring to the recent past — the previous day or the night just passed. It occurs only about four times in Scripture, appearing in passages that speak of what happened "just recently" or contrast past events with the present moment.
The rarity of emesh makes its appearances significant. In Job 30:3, the desolate men who mock Job "gnaw the parched land; they harvest the salt marshes by night (emesh)." The word marks temporal boundaries — what was, versus what is. Theologically, the fleeting nature of "yesterday" contrasts with God's eternal unchanging nature: "Jesus Christ is the same yesterday and today and forever" (Hebrews 13:8). Human yesterdays pass; God's faithfulness does not.